Magnetizers for pigging tools including a cushion

ABSTRACT

Circumferential and axial magnetizers for a magnetic flux leakage pig. A magnet bar may comprise at least one magnet and may be configured to collapse radially inward to the shaft. Magnetizers may include a cushion disposed about the shaft and biasing the magnet bar against a pipe wall. A sensor head disposed between circuit poles at each polar end of the magnet monitors magnetic flux. The central shaft of a circumferential magnetizer or axial magnetizer may comprise a joint linking an additional smart pig module. A novel magnetizer cushion is described, as are smart pigs containing one or more circumferential or axial magnetizers.

CROSS-REFERENCE

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/251,348 filed on Jan. 18, 2019, which is a divisionalapplication of U.S. patent application Ser. No. 15/674,973 filed on Aug.11, 2017, which in turn claims benefit under 35 U.S.C. § 119(e) ofProvisional U.S. Patent Application No. 62/373,902, filed Aug. 11, 2016and Provisional U.S. Patent Application No. 62/448,811, filed Jan. 20,2017. The contents of each foregoing application are incorporated hereinby reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to apparatus and systems for inspectingpipelines. More specifically, the present disclosure relates toapparatus and systems for detecting structural defects, flaws, and otherdamage in pipeline systems.

BACKGROUND

The energy infrastructure of the world depends on pipelines. Pipelinestransport crude oil and unrefined gas from wells to refineries andtransport refined products to chemical plants, utilities, localdistribution units, homes, airports, and nearly every place that usesenergy. Energy pipelines include liquid petroleum pipelines and naturalgas pipelines.

Pipelines can vary in size depending on purpose. For example, inoil-producing locations, gathering pipelines may be as small as twoinches in diameter. The Trans-Alaska Pipeline, in contrast, whichtransports crude oil, is about 48 inches in diameter. Pipelines ofvarying sizes and purposes have diameters in between.

Given the materials being transported, pipelines present health, safety,environmental, and security concerns. Pipeline and energy companies areeconomically incentivized to bring as much product as possible fromsource to destination. The various governments also regulate pipelinesand pipeline-transported materials extensively. To prevent release ofpipeline-transported materials, pipeline and energy companies conductintegrity management programs continuously.

Integrity management programs include inspections to determine theintegrity of pipeline systems. To this end, inspections may identifyearly indications of future problems, such as corrosion, cracks,mechanical damage, and dent and bend strain locations that may havedefects that can cause failures in the future. Pipeline inspectioncompanies have developed specialized tools to inspect the full body ofpipelines, including inline inspection tools commonly referred to assmart pigs.

Smart pigs travel through the interior of a pipeline, often withoutstopping the flow of medium through the pipeline. These pigs may collectgigabytes of data about a pipeline including wall thickness, geometricalshape, corrosion, pitting, cracks, holes, dents, and other potentialsources of problems. Identifiable flaws include, but are not limited to,metal loss caused by corrosion, erosion, pipe manufacturing, andconstruction of pipelines. These flaws may also include some forms ofaxially oriented flaws, such as narrow axial metal loss, hook cracks,lack of fusion, and fatigue-related cracking. These flaws may alsoinclude circumferentially oriented flaws of a similar nature. Mechanicaldamage may also be identified, including dents, gouges, cracks, andcombined defects (e.g., a gouge near a pipe seam), and these types ofdamage may also be oriented either axially or circumferentially. Pigsuse various, specialized sensing systems to automatically andcontinuously collect and store this data. Related software is typicallyused to interpret the data and aid operators in identifying significantflaws in order to investigate and make the necessary repairs to helpprevent failures.

Pigs used for in-line inspection of pipelines may employ one or more ofseveral technologies, including but are not limited to ultrasonictechnology (“UT”) for wall thickness measurements or crack detection,electromagnetic acoustic transducer (“EMAT”) technology, magnetic fluxleakage (“MFL”) technology, pipe surface profiling commonly referred toas geometry or caliper technology, and inertial mapping of pipelocations and detection of ground movement (“IMU”). MFL is anondestructive method of testing that employs a magnetic flux leakageprinciple to detect certain defects and potential problems found in thefull body of a pipeline. MFL can be used only in pipelines made offerromagnetic metals, such as carbon based steels. Powerful magnets,including permanent or electromagnets, magnetize portions of thepipeline, and sensors may be generally placed between the poles of themagnets to monitor the changes in flux leakage from the pipeline inareas experiencing various flaws where the cross sectional area isreduced by metal loss or where a fissure or crack perpendicular to thedirection of the magnetic field causes a detectable change in themagnetic leakage field. Automated feature searches and human analysiscan provide comprehensive reporting, prioritizing, and quantifying theseverity of flaws. This information is then used by the pipelineoperators to facilitate field investigations, repairs, and futureinspection intervals.

SUMMARY

The present disclosure relates to pigs utilizing magnetic flux leakagetechnology. An embodiment of the present disclosure relates to MFL pigshaving one or more circumferential magnetizers. Another embodiment ofthe present disclosure relates to MFL pigs having one or more axialmagnetizers. Yet another embodiment of the present disclosure relates toMFL pigs having at least one of a circumferential magnetizer and atleast one of an axial magnetizer.

A pig may be cylindrical in shape and sized to fit the diameter of thepipeline being inspected. A pig may include one or more componentbodies. Where a pig includes two or more component bodies, the componentbodies may be operatively connected. For example, an MFL pig may includethree or more component bodies operatively connected to each other, twoor more of the component bodies including magnetizers comprising magnetsand sensors, and another component body including batteries, datastorage, and various electronics. In some embodiments, a pig may includemore than three component bodies. For example, a pig may include threecircumferential magnetizers, an axial magnetizer, an electronics body, ageometry body, an IMU body, and a battery body. In an embodiment, theaxial or circumferential magnetizers may be offset from each other toprovide complete circumferential sensor coverage of the pipe.

A magnetizer on an MFL pig may use permanent magnets or electromagnets.In an embodiment, a magnetizer may use rare-earth magnets, for exampleneodymium-based magnets. Rare-earth magnets, such as neodymium-basedmagnets, may be plated with a metal layer. For example, neodymium-basedmagnets may be plated with a thin nickel layer.

In an embodiment, each magnetizer module may be arranged with four ormore magnet bars. In an embodiment, each magnetizer module may bearranged with six magnet bars. Each magnet bar may provide a localizedcircuit to bring the magnetic flux density in the pipe wall to nearsaturation levels. For example, the flux density in the pipe wall may bebrought equal to or greater than 1.6 Tesla. One of skill in the art willrecognize that the number, type, and location of the magnets or magnetbars may be altered in various ways and still achieve saturation, forexample, a magnetic flux density of about 1.6 Tesla.

Each of the magnet bars may be attached to a center shaft extendingabout a central axis of the magnetizer. The magnet bars may extendradially outward from the central shaft, which may have an axiscoextensive with the direction of the pipeline. A circumferentialmagnetizer may create a magnetic field orientation in a directiontransverse to the axis of a pipeline. An axial magnetizer may create amagnetic field orientation in a direction corresponding to the axis of apipeline.

Hall-effect sensors (or other high-sensitivity sensors), may be placedon each magnet bar between the north and south poles. The sensors, orthe sensor heads on which the sensors may be affixed, may be coupled tothe central shaft. These sensors may monitor the changes in the magneticfield, which may leak from the internal pipe surface. Changes in fluxleakage may occur at areas with corrosion or metal loss, geometricdeformations, dents, buckles, wrinkles, and different forms of cracking.Software and human analysis can identify damaged areas and determine theextent of damage. For example, the MFL pig and accompanying software anddata analysis may identify the length, width, depth, and location offlaws in the pipeline.

In an embodiment, the pig may include a plurality of sensors. In a moredetailed embodiment, the plurality of sensors may include at least oneHall sensor. In an alternate embodiment, the plurality of sensors mayinclude at least one ultrasonic or eddy-current sensor. Some embodimentsmay include one or more Hall-effect sensors and one or more ultrasonicor eddy-current sensors. In an embodiment, one or more sensors may bedisposed on a sensor head, which may have a sloping trapezoid, rhomboid,rectangle, or parallelogram shape.

A sensor head may include a suspension system for positioning andbiasing the sensor head. In an embodiment, a sensor head may bepositioned and biased with one or more conical springs to allowcontinuous tracking of the internal surface of the pipe. In anembodiment, a plurality of sensors may be disposed on an articulating,radial floating sensor head to continuously track the surface of thepipeline.

In an embodiment, a pig according to the present disclosure may includeone or more magnet bar wear pads. A magnet bar wear pad, in anembodiment, may be arranged and designed to facilitate slowcounter-clockwise rotation of a magnetizer or pig.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features of the present disclosure will becomemore fully apparent from the following description, taken in conjunctionwith the accompanying drawings. Understanding that these drawings depictonly several embodiments in accordance with the disclosure and aretherefore, not to be considered limiting of its scope. The disclosurewill be described with additional specificity and detail through use ofthe accompanying drawings.

In the drawings:

FIG. 1 depicts an MFL pig having a plurality of operatively connectedcomponent bodies in accordance with an embodiment of the presentdisclosure;

FIG. 2 presents a side view of a portion of an MFL pig having aplurality of operatively connected component bodies in accordance withan embodiment of the present disclosure;

FIG. 3 is a sectional schematic diagram of a circumferential magnetizer;

FIG. 4 depicts a schematic diagram of a magnet bar and shows thedirection of the magnetic field in relation to the sensors and acrack-like defect, in accordance with an embodiment of the presentdisclosure;

FIG. 5 presents an illustration of sensor placement relative to magnetand magnet bar placement on a circumferential magnetizer in accordancewith an embodiment of the present disclosure;

FIG. 6 shows a top view of a circumferential magnet bar in accordancewith an embodiment of the present disclosure;

FIG. 7 depicts a perspective view of a circumferential magnetizer inaccordance with an embodiment of the present disclosure;

FIG. 8 shows a plurality of circumferential magnetizers according to anembodiment of the present disclosure operatively linked together andnavigating bends in a pipeline;

FIG. 9 shows a plurality of circumferential magnetizers and theirmechanical relationship to each other according to an embodiment of thepresent disclosure;

FIG. 10 shows perspective views of two circumferential magnetizers toillustrate the relationship of the magnet bars according to anembodiment of the present disclosure;

FIG. 11 shows the suspension system of the magnet bars and illustratesthe ability of the magnet bars to track the pipe surface according to anembodiment of the present disclosure;

FIG. 12 presents a side perspective view of a circumferential magnetizeraccording to an embodiment of the present disclosure;

FIG. 13 shows a cross sectional view of one of the magnetizer modulesshowing key components of the design, according to an embodiment of thepresent disclosure;

FIG. 14 shows a side view of an embodiment of a circumferentialmagnetizer with a magnet bar removed to illustrate certain features;

FIG. 15 shows a cross-section of a side view of a circumferentialmagnetizer in accordance with an embodiment of the present disclosure;

FIG. 16 shows exemplary axial magnetizer modules coupled together inaccordance with an embodiment of the present disclosure;

FIG. 17 shows front and side views of an exemplary axial magnetizer inaccordance with an embodiment of the present disclosure;

FIG. 18 shows a side view of an embodiment of an axial magnetizer with amagnet bar removed to illustrate certain features;

FIG. 19 a cross-section of a side view of an axial magnetizer inaccordance with an embodiment of the present disclosure;

FIG. 20 is a sectional view of a portion of a portion of a smart pigincluding magnetizer modules in accordance with an embodiment of thepresent disclosure;

FIG. 21 is a front view of a magnetizer cushion for an axial magnetizeror a circumferential magnetizer in accordance with an embodiment of thepresent disclosure;

FIG. 22 is a front view of a section of a circumferential magnetizerincorporating a magnetizer cushion in accordance with an embodiment ofthe present disclosure;

FIG. 23 is a side view of a section of a circumferential magnetizerincorporating a magnetizer cushion in accordance with an embodiment ofthe present disclosure;

FIG. 24 is a side view of a magnetizer cushion for a circumferentialmagnetizer along with forward and aft spacers in accordance with anembodiment of the present disclosure;

FIG. 25 is a front view of a section of an axial magnetizerincorporating a magnetizer cushion in accordance with an embodiment ofthe present disclosure;

FIG. 26 is a side view of a magnetizer cushion for an axial magnetizerin accordance with an embodiment of the present disclosure;

FIG. 27 is a front view of a magnetizer cushion for an axial magnetizerin accordance with an embodiment of the present disclosure;

FIG. 28 is a side view of a section of an axial magnetizer incorporatinga magnetizer cushion in accordance with an embodiment of the presentdisclosure;

FIG. 29 is a side view of a magnetizer cushion for an axial magnetizeror a circumferential magnetizer in accordance with an embodiment of thepresent disclosure; and

FIG. 30 is an isometric view of an axial magnetizer in accordance withan embodiment of the present disclosure.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described herein arenot meant to be limiting. Other embodiments may be utilized, and otherchanges may be made, without departing from the spirit or scope of thesubject matter presented here. It will be readily understood that theaspects of the present disclosure, as generally described herein, andillustrated in the Figures, may be arranged, substituted, combined, anddesigned in a wide variety of different configurations, all of which areexplicitly contemplated and make part of this disclosure.

This disclosure is generally drawn to apparatus and systems forinspecting pipelines. Examples of this disclosure may be drawn to pigsand pigging systems, smart pigs, MFL pigs, circumferential magnetizersfor MFL pigs, and axial magnetizers for MFL pigs. Particular examplesmay be directed to certain aspects and components of circumferentialmagnetizers for MFL pigs, including sensor heads, suspension systems forthe sensor heads, magnet bar wear pads, and the like. Additionalexamples may be directed to certain aspects and components of axialmagnetizers for MFL pigs, including sensor heads, suspension systems forthe sensor heads, magnet bar wear pads, and the like.

With reference to FIG. 1, an exemplary embodiment of an MFL pigincluding circumferential magnetizers is shown. The MFL pig may includeseveral component bodies, including circumferential magnetizers 101,integrated electronic component body 102, and drive section componentbody 103. Each of circumferential magnetizers 101 may be offset from theother in order to ensure that the entire pipe surface to be inspected iscovered by the magnetic circuits and sensors. A geometry module 104 mayinclude mechanical arms for measuring deformations and the internaldiameter of the pipeline. An additional module 105 may include aninertial measurement unit for continuous mapping of the pipeline. One ormore battery modules 106 may be used to power all systems related to theinspection tool. A rear assembly module 107 may contain a transmitterand odometer. As will be appreciated by one of skill in the art, variousother sensors and electronic components may be included on an MFL pigdepending on the purpose of the pig and the intended measurements.

FIG. 2 presents a detailed view of the exemplary embodiment of the MFLpig shown in FIG. 1. The portion of the MFL pig shown in the embodimentof FIG. 2 includes three circumferential magnetizer modules 101. One ofskill in the art will appreciate that the component bodies shown neednot be in the particular order presented in the figure. The modularstructure of the component bodies may also enable easy repair of the pigby allowing a technician to swap out a component body in need of repair,thus allowing the pig to remain in service more continuously.

A circumferential magnetizer 101 in accordance with the presentdisclosure may include several components, including magnet systems,sensor systems, sensor suspension systems, magnet bar wear pads, andother related components. A circumferential magnetizer in accordancewith the present disclosure may include one or more magnets oriented andconfigured to induce a magnetic field transverse to the axis of thepipeline. In an embodiment, a magnetizer may include a plurality ofbanks of magnets disposed circumferentially around a central shaft of amagnetizer. In an embodiment, sensors may be disposed between the banksof magnets.

FIG. 3 presents a sectional schematic diagram of a circumferentialmagnetizer. Circumferential magnetizer 300 may include magnets 301,magnetic circuit poles 302, and sensors 304. Each magnet 301 andcorresponding magnetic circuit poles 302 may form a magnet bar. Theposition of the sensors 304 relative to the pipe wall and within themagnetic circuit can be seen. FIG. 3 illustrates the location 303 offlux leakage from the pipe wall and its relationship to the sensors.This diagram illustrates the general layout of components ofcircumferential magnetizer 300 and is not necessarily drawn to scale. Aswill be appreciated by one of skill in the art, magnetic flux 303 willnot be visible, but its position is included for descriptive purposes.Magnets 301 may be disposed at several locations in a circumferentialdirection about circumferential magnetizer 300. Magnets 301 may includeone or more banks of magnets at each location. For example, FIG. 3illustrates magnets 301 at six circumferential locations; each locationmay include one or more magnets 301 extending axially, which is notvisible from the sectional schematic drawing. Magnetic circuit poles 302may be provided to impart magnetic flux from magnets 301 to the interiorof a pipe and thereby magnetize the pipe wall. Separate wear inserts maybe coupled to magnetic circuit poles 302 to extend the wear life of themag bars. Sensors 304 may be positioned between magnetic circuit poles302 to monitor the magnetic flux through the pipe wall and detectmagnetic flux leakage.

As described above, a circumferential magnetizer may include a pluralityof magnets or a plurality of banks of magnets. The magnets, togetherwith the magnetic circuit poles, may form magnet bars. The magnet barsmay be spaced evenly apart from each other and may extend radiallyoutward from the central shaft, the central shaft being coaxial with thelength of the pipeline. For example, a circumferential magnetizer mayinclude two or more magnet bars, each magnet bar having a pair ofmagnetic circuit poles with the sensors disposed between the magneticcircuit poles. The sensor head may include a plurality of sensors. Themagnet bars may include a plurality of magnets, each magnet beingaligned in the same polarity. A magnetic circuit pole may contact onepole of a magnet and extend from the magnet radially outward toward apipe wall. Another magnetic circuit pole may contact the opposite poleof the magnet and extend from the magnet radially outward toward thepipe wall. A sensor head may be disposed between these magnetic circuitpoles. In this manner, a magnetic field may flow between the magneticcircuit poles and across the sensor head disposed between the magnetbars. When the magnetic circuit poles contact the pipe wall, a magneticcircuit may be created, and the sensors on the sensor head may monitorthe magnetic flux and detect any magnetic flux leakage from the pipewall.

In an embodiment, a circumferential magnetizer may include two or moremagnet bars, each including one or more magnets. In an embodiment, eachmagnet bar may include a plurality of magnets, each magnet having thesame orientation. Each magnet may include a first side having a firstpolarity and a second side having a polarity opposite to the firstpolarity. A first magnetic circuit pole may extend radially outward fromthe side of a magnet having a first polarity toward the pipe wall, and asecond magnetic circuit pole may extend radially outward from the sideof a magnet having the opposite polarity toward the pipe wall.Positioning magnets and magnetic circuit poles in this manner allows amagnetizer to impart a magnetic field circumferentially around theinterior of a pipeline in an orientation transverse to the axis of thepipeline. This orientation may allow for axially oriented defects, suchas a narrow axial metal loss or corrosion, loci of damage, some forms ofaxial cracking, or longitudinal seam weld defects extending axially downa portion of the pipeline to be detected.

The magnets in a circumferential magnetizer may be permanent magnets orelectromagnetic magnets. In an embodiment, the magnets may be rare-earthpermanent magnets. In an embodiment, the magnets may be neodymium-basedmagnets.

Each magnetic circuit pole may include one or more wear pads. A magneticcircuit pole wear pad may protect a magnetic circuit pole from theinterior surface of the pipeline or debris within the pipeline interior.This may extend the amount of usable time between repairs. In anembodiment, a magnetic circuit pole wear pad may comprise one or moreinserts. In a detailed embodiment, the magnetic circuit pole wear padmay comprise a plurality of carbide or ceramic inserts. In anembodiment, one or more magnetic circuit poles may include one or morecarbide or ceramic inserts disposed directly into the magnetic circuitpole(s). Carbide or ceramic inserts may provide beneficial reductions indrag force. Carbide or ceramic inserts may reduce drag force by as muchas 30% from conventional designs. Each magnetic circuit pole wear pad,if included, may be maintained at an angle with respect to the axis ofthe pipeline. A magnet bar wear pad, in an embodiment, may be arrangedand designed to facilitate slow counter-clockwise rotation of amagnetizer or pig. Alternatively or in addition, the carbide or ceramicinserts, if included, may be disposed in a pattern designed tofacilitate a slow rotation of the pig.

One or more sensor heads may be placed in each magnet bar. The one ormore sensor heads may be disposed between magnetic circuit poles and maytherefore be positioned to measure magnetic flux through a pipe wall.Each sensor head may include one or more sensors. The magnets maysaturate a portion of pipeline to be inspected with a circumferentialmagnetic field. The sensors may measure the magnetic field and, inparticular, may detect changes or aberrations in the magnetic field.Defects in the pipeline, including corroded areas, areas missing metal,geometric deformations, dents, buckles, wrinkles, cracks, and the likemay induce aberrations and changes into the magnetic field, or themagnetic field may leak at the particular location of a defect.

For example, FIG. 4 depicts a single magnet bar. Each magnet bar mayinclude magnets having a first polarity 401 (e.g., a south pole) and asecond polarity 402 (e.g., a north pole) opposite to the first polarity401. Note that the nomenclature and particular polarity assigned for thepurposes of the written description is largely arbitrary; for example,north could be called positive, and south could be called negative. Asouth magnetic circuit pole 401 may couple the south pole side of themagnets to the pipe wall, and a north magnetic circuit pole 402 maycouple the north pole side of the magnets to the pipe wall. Further, itis important that a sensor head be flanked on either side by magneticcircuit poles of opposing polarities to establish a magnetic fieldextending over and through the sensor head and sensors; this will beexplained in further detail later.

The circumferential magnetizers may travel through a pipe having aninternal diameter less than the nominal diameter of the magnetizer andmay be configured to closely articulate with the pipe wall. A pipe mayhave some structural aberration, such as a crack or crack-like anomaly.The magnetic field from the magnets may be imparted to the pipe wall bysouth magnetic circuit pole 401 and north magnetic circuit pole 402. Forvisualization and descriptive purposes, magnetic flux lines 403 aresuperimposed onto the diagram. Sensors may be placed between magnets tobe within the magnetic field. The magnetic field may be disrupted whenthe circumferential magnetizer passes over an aberration, and thedisruption in the magnetic field may be detected by the sensors. Arrow405 represents a direction of travel through a pipe.

In an embodiment, a magnet bar may include a plurality of sensorsbetween each magnetic circuit pole to measure the magnetic flux impartedinto the pipe. FIG. 5 generally illustrates the placement of sensorsrelative to the magnets. FIG. 5 shows a circumferential magnetizerhaving magnets 501, magnetic circuit poles 502, and sensors 503. Sensors503 may be positioned between magnetic circuit poles 502. Magneticcircuit poles 502 may impart a magnetic flux into a pipe wall, and themagnetic flux may flow from one magnetic circuit pole to the other.Sensors 503 positioned within the magnetic field may take measurementsof the magnetic flux. In an embodiment, sensors 503 may takemeasurements of the magnetic flux as closely as every 0.039″ (1 mm) inthe axial direction of the pipe. In an embodiment, sensors 503 may takemeasurements of the magnetic flux as closely as every 0.050″ (1.25 mm)in the axial direction of the pipe. In an embodiment, sensors 503 maycomprise Hall-effect sensors. In an embodiment, a circumferentialmagnetizer may include six magnet bars and may have 72 Hall sensors perdiameter-inch. Aberrations in the pipe may cause distortions ordisruptions in the magnetic field, and the sensors may thus detect theirregularities in the magnetic field corresponding to the aberration inthe pipe. A magnetizer utilizing a circumferentially oriented magneticfield may be particularly adept at detecting axially oriented flaws andinspecting longitudinal welds of a pipeline. A magnetizer utilizing acircumferentially oriented magnetic field may be able to detect flaws of0.8 inches (20 mm) with an opening of 0.004″ (0.1 mm). A sensor head maybe able to survive forces of up to about 20 G, and sensors may be ableto withstand pressures of up to 2,000 psi (13.8 Mpa) and velocities ofup to 30 ft/s (9 m/s).

In an embodiment, each sensor head may include a plurality of sensors503. The plurality of sensors 503 may include Hall-effect sensors,eddy-current sensors, ultrasonic sensors (such as EMAT sensors), orcombinations thereof. The responses of each sensor may be combined andanalyzed to locate or define certain pipeline defects, as discussedabove. For example, a Hall-effect sensor may detect a response to amagnetic field leakage. The output of a Hall-effect sensor may varylinearly or nonlinearly with respect to changes in the magnetic field.These changes may reflect the presence of a flaw, defect, or anomaly.The output of a plurality of such sensors, in the aggregate, may allowfor an ultra-high resolution sampling in a given area of the internalpipe surface, thereby allowing defects to be accurately detected,characterized, analyzed, and quantified. In an embodiment, acircumferential magnetizer according to an aspect of the presentdisclosure may measure and store flux leakage values to a samplingdensity of up to 500 per square inch (80 square cm). In an embodiment, acircumferential magnetizer according to the present disclosure mayinclude several sensor heads, each sensor head having a plurality ofindividual sensors. In an embodiment, a pig may include threecircumferential magnetizer modules with six sensor heads per module and24 Hall-effect sensors per sensor head. This exemplary embodiment wouldyield a total of 432 Hall-effect sensors on the circumferentialmagnetizer. In an exemplary embodiment, a smart pig may have a diametergreater than six inches and contain three circumferential magnetizermodules, wherein each module includes six sensor heads and each sensorhead includes 24 Hall-effect sensors. Such a circumferential magnetizercould be said to have a sensor density of 72 sensors per diameter-inch.In an embodiment, a circumferential magnetizer may have a sensor densityof between about 60 to 100 sensors per diameter-inch.

A circumferential magnetizer may be sized to have a nominal diameterslightly larger than the diameter of a pipe. For example, acircumferential magnetizer slightly larger than six inches in diametermay be configured to travel through a six-inch pipe. One of skill in theart will recognize that a circumferential magnetizer according to thepresent disclosure may be sized to inspect pipes of alternate diameters.

FIG. 6 shows a top view of a magnet bar of a circumferential magnetizerin accordance with an embodiment of the present disclosure. In theembodiment shown in FIG. 6, a circumferential magnetizer may include anorth magnetic circuit pole 601 extending from a north-polarity side ofone or more magnets and a south magnetic circuit pole 602 extending froma south-polarity side of one or more magnets. When north magneticcircuit pole 601 and south magnetic circuit pole 602 contact a pipewall, a magnetic flux may extend between magnetic circuit poles 601,602. Sensor head 603 may be disposed between magnetic circuit poles 601,602. Sensor head 603 may include one or more sensors 604. In anembodiment, sensors 604 may be Hall-effect sensors. In an embodiment,there may be 24 sensors 604 disposed on sensor head 603. In anembodiment, the magnet bar of FIG. 6 may include one or more magnets. Inan embodiment, the magnet bar of FIG. 6 may include three magnets.

Magnetic circuit poles 601, 602 may contact the interior of thepipeline. In an embodiment, magnetic circuit poles 601, 602 may functionas a flux coupler to more efficiently saturate a pipe wall with amagnetic field. In a detailed embodiment, magnetic circuit poles 601,602 may include wear pads 605 on at least a portion of a surface thatcontacts the pipe wall. Wear pads 605 may comprise one or more ceramicor carbide inserts, as depicted in FIG. 6. Ceramic or carbide insertsmay protect the magnetic circuit poles from wear and may reduce dragforce. In an embodiment, ceramic or carbide inserts may reduce dragforce by about 30%.

FIG. 7 depicts a perspective view of a circumferential magnetizer inaccordance with an embodiment of the present disclosure. In theembodiment shown in FIG. 7, a circumferential magnetizer may includenorth magnetic circuit pole 701 extending from a north-polarity side ofone or more magnets, south magnetic circuit pole 702 extending from asouth-polarity side of one or more magnets, sensor head 703, and aplurality of sensors 704 disposed on sensor head 703. In an embodiment,sensors 704 may be Hall-effect sensors, and there may be 24 sensors 704disposed on sensor head 703. A sensor head wear pad 705 may be coupledto sensor head 703. Sensor head wear pad 705 may articulate with thepipe and may function to protect sensors 704.

Sensor head wear pad 705 may comprise a nickel-based alloy orsuperalloy. Magnetic circuit poles 701, 702 may include a ceramic insertor coating. In detailed embodiments, the ceramic may comprise siliconcarbide. In alternate detailed embodiments, the inserts may comprisetungsten carbide.

The circumferential magnetizer according to the embodiment depicted inFIG. 7 may include a means for collapsing 706 magnetic circuit poles701, 702. Means for collapsing 706 may comprise front links 707, upperlink 709, and torsion spring 708. Means for collapsing 706 may exert asufficient force, such as a spring force, to maintain the magneticcircuit poles 701, 702 in engagement with the pipe wall but maycollapse, entirely or partially, if the magnetic circuit poles 701, 702encounter an aberration in the pipe, such as an indentation, or if thepig including the circumferential magnetizer encounters a bend in thepipe. In an embodiment, sensor head 703 is also operatively coupled tothe means for collapsing 706.

In an embodiment, a magnetizer may include a polyurethane cushiondisposed between a central shaft and one or more magnet bars. In oneaspect, a polyurethane cushion may be annular and may be disposedcircumferentially about the central shaft. In another aspect, multiplepolyurethane cushions may be disposed about one or more circumferentialportions of the central shaft. In one aspect, the one or morepolyurethane cushions may be disposed at one axial end of a magnet bar.In another aspect, the more or more polyurethane cushions may bedisposed circumferentially about the central shaft at each axial end ofa magnet bar. In an embodiment, a magnetizer having a polyurethanecushion might not have a torsion spring 708; rather, a magnetizer maycomprise front links 707, upper link 709, and the polyurethane cushion.The magnetizer cushion may provide a force sufficient to bias one ormore magnet bars toward a pipe wall. The magnetizer cushion may beconstructed or configured to have a pre-determined hardness andcollapsibility. In an embodiment, a magnetizer cushion (e.g., amagnetizer cushion made from polyurethane) may have a Shore durometer offrom about 70 A to about 90 A. In another embodiment, a magnetizercushion may have a Shore durometer of from about 75 A to about 85 A.

A magnetizer cushion (e.g., a polyurethane cushion) may present a numberof advantages for biasing one or more magnet bars against a pipe wallcompared to a spring (e.g., a steel torsion spring). First, a magnetizercushion (e.g., a polyurethane cushion) may provide a force on the magnetbar that biases the magnet bar against the pipe wall, but the magnitudeof force provided by the magnetizer cushion may be substantially lessthan the force imparted to the magnet bar by a spring (e.g., a nearneutral force). In an embodiment, a magnetizer cushion may impart aforce on a magnet bar from about 20% to about 30% less than the forcethat would be applied by a steel spring. With a lesser force, the dragexperienced by a magnetizer or a pig incorporating a magnetizer may bereduced. Moreover, with a lesser force, the amount of wear suffered bymagnetizer and/or magnet bar components is reduced. Second, a magnetizercushion may absorb vibrations or may better absorb vibrations, therebyimproving the quality of the data gathered by the sensors and improvingdetection of pipe defects. Third, a magnetizer cushion may better absorbforces from high-impact events, preventing damage to the magnetizers.Fourth, a magnetizer cushion may be able to be swapped with a magnetizercushion having a different hardness (e.g., a cushion made from adifferent type of polyurethane or a different thermoset or thermoplasticmaterial), so a user may be able to control the ride height and sagfactor, which can better tailor the magnetizer for different pipelinesor different environments. Fifth, a magnetizer cushion may provideadditional protection for electronic wiring (e.g., from shear forces,twisting, or pressure), which maybe passed through the lower portion ofthe cushion. Sixth, a magnetizer cushion may simplify the design of themagnetizer component that biases the magnet bar against the pipe wall;specifically, some spring designs are relatively complex, subjecting thesprings to maintenance (e.g., replacement, inspection, cleaning). Amagnetizer cushion may have an extended life, and may requiresignificantly less cleaning, reducing maintenance burdens and reducingthe risk of component failure. Seventh, spring designs (specifically inlarger tools) can be costly; a magnetizer cushion may cost a fraction ofa relatively more complicated spring. Incorporating a magnetizercushion, therefore, may reduce manufacturing costs and may reduce thecost of ownership long term. Eighth, many spring designs have complexshapes, and debris may build up in and around the spring over time,reducing the function of the spring and requiring additional ongoingmaintenance. A magnetizer cushion (e.g., a polyurethane cushion) mayreduce or eliminate such build up due to its simpler shape and how ittakes up space where debris may have previously built up.

In an alternate embodiment, sensor head 703 includes an independentsensor head suspension system. Sensor head suspension system may includeone or more conical springs coupling the bottom of the sensor head 703to the central shaft. In an embodiment, sensor head suspension systemcomprises dual conical springs. Both means for collapsing 706 and sensorhead suspension system may enable components of the circumferentialmagnetizer to collapse up to 25% of the outside diameter of the pipe;that is, the diameter of at least part of the circumferential magnetizermay be reduced by up to 25% when encountering an aberration in the pipeor when going around a bend in the pipeline. These features may allow apig to navigate pipeline bends of greater than or equal to 1.5 D (whereD is equal to the pipe diameter). In an embodiment, these features mayallow a pig to navigate pair of 1.5 D bends separated by a pipelinedistance equal to 3 D. The collapsibility features may reduce drag forceon the circumferential magnetizer, which may help to prevent a pig fromstalling when navigating a relatively tight bend.

FIG. 8 shows a plurality of circumferential magnetizers according to anembodiment of the present disclosure operatively linked togethernavigating bends in a pipeline. A plurality of circumferentialmagnetizers 804 may be operatively linked together by linking means 805.Linking means 805 may be able to rotate about the center shaft and mayinclude features allowing for some transverse rotation about a boltincorporated in the linking means. These features of linking means 805can be seen with reference to FIG. 8. Each circumferential magnetizer804 may include a plurality of magnet bars 807. Each magnet bar 807 mayinclude magnetic circuit poles and one or more sensor head(s) 806including a plurality of sensors. A pig including circumferentialmagnetizers 804 may be capable of navigating complex bends in a pipeline801. For example, each bend 802, 803 may have a bend configuration ofgreater than or equal to about 1.5 D. In an embodiment, each bend 802,803 may have a bend configuration with a pair of 1.5 D bends separatedfrom each other by a pipeline distance equal to 3 D. Circumferentialmagnetizers 804 may have a diameter of about six inches. If pipeline 801has a nominal diameter of six inches, there may be a distance of about18 inches between the bends 802, 803. Generally speaking,circumferential magnetizers 804 according to at least one embodiment ofthe present disclosure may be capable of navigating two bends 802, 803,where one magnetizer 804 simultaneously navigates each bend, if eachbend is separated by a distance of about three times the nominaldiameter of the pipe. A number of features may contribute to the abilityof a pig including three circumferential magnetizers to navigate suchcomplex bends without stalling, including but not limited to the meansfor collapsing the magnet bar (or the magnetizer cushion), which mayprovide the circumferential magnetizers with a collapsibility of about25%; the length of the magnet bars and the center shaft; and the designof the universal joints, which provide connections among the variousmodules comprising the smart pig. These features may be seen withreference to FIG. 8.

A smart pig may be propelled through a pipe while product is movingthrough the pipe. The moving product may exert a pressure on an aft endof a smart pig, or on the aft end of one or more modules comprising asmart pig, which may propel the pig through the pipe. The speed at whicha pig and its constituent modules travels is accordingly a result of thedifferential pressure at an aft end of the pig compared to the forwardend of the pig. To take consistent measurements, it is desirable tomaintain the differential pressure as close to constant as possible tokeep the speed of the pig as close to constant as possible. Whenencountering a bend in a pipeline, conventional pigs tend to experienceincreased drag force that slows down and often stalls the pig in thepipeline. When a pig stalls, the differential pressure at the aft end ofthe pig builds until the pig is shot free. However, a pig that is shotin such a manner may be travelling too fast to take reliablemeasurements. This speed may also increase the risk of damage. The meansfor collapsing, magnetizer cushion, or polyurethane ring and the carbidewear inserts coupled to the magnetic circuit poles of circumferentialmagnetizer of the present disclosure may help to reduce the drag forceexperienced in a bend, allowing the circumferential magnetizer modulesto maintain a constant speed through a bend, which may further enablemore accurate measurements to be taken throughout the pipeline,particularly in areas right after a bend. In an embodiment, a smart pigincluding three circumferential magnetizers may be able to navigate apair of 1.5 D bends separated from each other by a pipeline distanceequal to 3 D.

FIG. 9 depicts the three circumferential magnetizers 901.Circumferential magnetizers 901 may be connected to each other withuniversal joints 903, which are connected to the central shaft bylinkage components 902. The universal joints may be angle controlled.The circumferential magnetizers 901 may be oriented relative to eachother to ensure complete, 360-degree coverage of the inside of a pipe.Universal joints 903 may maintain the orientations of thecircumferential magnetizers with respect to each other. The centralshaft, linkage components 902, and universal joints 903 may comprisetitanium to maintain strength, provide corrosion resistance, and reduceweight. In an embodiment, the central shaft, linkage components 902, anduniversal joints 903 may be comprised entirely of titanium.

FIG. 10 includes a front view 1001 and an isometric view 1002 of acircumferential magnetizer module according to an embodiment of thepresent disclosure. FIG. 10 shows that each module may have six magnetbars, each with a magnet 1003. Each magnet bar may provide approximately20 degrees of pipe wall coverage. Three such modules may allow a pig toprovide 360-degree coverage. Providing a smart pig with three modulesmay, for example, allow complete coverage in a six-inch pipe, but othertool diameters may require a different number of bars or modules.

FIG. 11 provides a side view of a circumferential magnetizer moduleshowing just two bars and their respective means for collapsing. Meansfor collapsing includes upper and lower parallel links 1101, which jointhe magnet bars 1102 to the central shaft 1104. The parallel linksensure that the magnet bars 1102 continually remain in good contact andparallel to the pipe surface and central shaft 1104. The torsion springs1103 mounted on the upper link of each magnet bar keep the modulecentered and allow the magnet bars to collapse toward central shaft 1104when passing over obstacles or negotiating bends and other borerestrictions. In an alternate embodiment, a magnetizer may include amagnetizer cushion disposed between a central shaft and one or moremagnet bars. In an embodiment, the magnetizer cushion may be formed froma polyurethane. In one aspect, a polyurethane cushion may be annular andmay be disposed circumferentially about the central shaft. In anotheraspect, multiple polyurethane cushions may be disposed about one or morecircumferential portions of the central shaft. In one aspect, the one ormore polyurethane cushions may be disposed at one axial end of a magnetbar. In another aspect, the more or more polyurethane cushions may bedisposed circumferentially about the central shaft at each axial end ofa magnet bar. In an embodiment, a magnetizer having a polyurethanecushion might not have a torsion spring 708; rather, a magnetizer maycomprise front links 707, upper link 709, and the polyurethane cushion.The polyurethane cushion may provide a force sufficient to bias one ormore magnet bars toward a pipe wall. The polyurethane cushion may beconstructed or configured to have a pre-determined hardness andcollapsibility.

In an embodiment, each magnet bar may include rear links similar tolinks 1101 to join the rear end of each magnet bar to the central shaft1104, along with a torsion spring or a magnetizer cushion. Such anembodiment may maintain the entire magnet bar in contact with the pipewall. Alternatively, as shown in FIG. 14, each magnet bar 1404 of acircumferential magnetizer may include a front control link 1401 and atorsion spring 1402 or a magnetizer cushion, as depicted in FIG. 20.Torsion spring 1402 or the magnetizer cushion may support the weight ofeach magnet bar and may help to support the weight of the central shaft.The rear portion of a circumferential magnetizer may additionallyinclude a polyurethane ring 1403. Polyurethane ring 1403 may help tomaintain each magnet bar biased against the pipe wall but may also helpto balance forces, especially when encountering aberrations in thepipeline or when navigating bends. Polyurethane ring 1403 may includebends, which may allow polyurethane ring 1403 to temporarily collapseand allow the magnet bar(s) 1404 to collapse toward the center shaft.Ring 1403 may be made from polyurethane for durability and chemicalresistance concerns; however, one of skill in the art may recognizealternative materials from which ring 1403 may be constructed, such assilicone or a durable, chemical-resistant thermoplastic.

FIG. 12 illustrates a side view of circumferential magnetizer module.The circumferential magnetizer according to the embodiment of FIG. 12includes magnetic circuit poles 1201. Magnetic circuit poles 1201 may becurved and thickened at their forward and aft ends. Magnetic circuitpoles 1201 may include wear pads 1202. The curvature and end thickening,which is visible in FIG. 12, may help to concentrate the magnetic fluxand create greater magnetic uniformity across sensor head 1203. Sensorhead 1203 may include a wear plate and may include a single attachmentpoint. The single attachment point may facilitate both radial movementand internal surface curvature tracking.

FIG. 13 provides a sectional view of a circumferential magnetizer moduleaccording to an embodiment of the present disclosure. Thecircumferential magnetizer module may include a hollow central shaft1301, front universal joint 1302, rear universal joint 1303, magnets1304, magnet shields 1305, and upper and lower magnet bar to centershaft attachment links 1306, 1307. A circumferential magnetizer modulemay include a sensor head base plate 1314, a sensor head 1311, aplurality of sensors 1312 disposed on sensor head 1311, a wear pad 1313,and conical springs 1308 for suspension of the sensor head 1311. FIG. 13also illustrates the location of torsion spring 1310. Central shaft 1301may extend to universal joint limiter 1315, which limits the movement ofthe universal joints 1303 and keeps the magnetizers in properorientation with respect to one another to maintain 360-degree pipe wallcoverage.

A sensor head 1311 may be in the shape of a sloping trapezoid. Theapproach angle of a sensor head according to such a design may minimizethe transmission of mechanical shocks and vibrations to the sensors andelectronics. Furthermore, such a sensor head design may provide a longerwear life, which may contribute to a longer inspection time of a smartpig between repairs. In an embodiment, one or more sensor heads 1311 mayextend radially outward and articulate with a surface of a pipeline totrack the pipeline surface. In an alternate embodiment, sensor head 1311may be shaped as a parallelogram or a rhomboid.

FIG. 15 presents a cross-sectional side view of an embodiment of acircumferential magnetizer including features already described herein.A plurality of magnet bars 1309 are attached to a central shaft 1501through a means for collapsing 706. The means for collapsing maycomprise a torsion spring 1310; instead, an annular magnetizer cushion(e.g., a polyurethane cushion) may be disposed about the central shaft1502 and may maintain the magnet bars 1309 biased against a pipe wall.Each magnet bar may include a sensor head 1311, a plurality of sensors1312 disposed on sensor head 1311, a wear pad 1313, a sensor head baseplate 1502, magnets 1304, magnet shields 1305, and conical springs 1308for suspension of the sensor head 1311.

An MFL pig, in addition to or as an alternative to one or morecircumferential magnetizers, may include one or more axial magnetizers.An axial magnetizer in accordance with the present disclosure mayinclude several components, including magnet systems, sensor systems,sensor suspension systems, magnet bar wear pads, and other relatedcomponents. An axial magnetizer in accordance with the presentdisclosure may include one or more magnets oriented and configured toinduce a magnetic field coaxially with the axis of the pipeline. In anembodiment, an axial magnetizer may include a plurality of magnets of afirst polarity disposed circumferentially around a front end of acentral shaft as well as a plurality of magnets of the opposite polaritydisposed circumferentially around a rear end of the central shaft. In anembodiment, sensors may be disposed between the magnets having oppositepolarities.

With reference to FIG. 16, which shows two axial magnetizers 1601coupled together, an axial magnetizer may include a plurality of magnets1602, which may be coupled to the pipe wall with magnetic circuit poles1603, 1604. The magnets 1602, together with the magnetic circuit poles1603, 1604, may form magnet bars. The magnet bars may be spaced evenlyapart from each other and may extend radially outward from the centralshaft, the central shaft being coaxial with the length of the pipeline.For example, an axial magnetizer may include two or more magnet bars. Inan embodiment, an axial magnetizer may include six magnet bars. Eachmagnet bar may have a pair of magnetic circuit poles 1603, 1604 withsensors 1606 disposed between the magnetic circuit poles 1603, 1604. Asensor head 1605 may include a plurality of sensors 1606. Each magnetbar may include a magnet 1602A disposed toward the front end of themagnet bar having a first polarity and a magnet 1602B disposed towardthe rear end of the magnet bar having the opposite polarity. A frontmagnetic circuit pole 1603 may contact the first pole of the frontmagnet 1602A and extend from the magnet 1602A radially outward toward apipe wall. A rear magnetic circuit pole 1604 may contact the oppositepole (i.e., the opposite pole of the front magnet) of the rear magnet1602B and extend from the magnet 1602B radially outward toward the pipewall. A sensor head 1605 may be disposed between these magnetic circuitpoles. In this manner, a magnetic field may flow between the magneticcircuit poles and across the sensor head 1605 disposed between themagnet bars. When the magnetic circuit poles contact the pipe wall, amagnetic circuit may be created, and the sensors 1606 on the sensor head1605 may monitor the magnetic flux and detect any magnetic flux leakagefrom the pipe wall. Positioning magnets 1602 and magnetic circuit poles1603, 1604 in this manner allows a magnetizer to impart a magnetic fieldin an axial direction with respect to the axis of the pipeline. Thisorientation may allow for circumferentially oriented defects, such as ametal loss or corrosion at girth welds, loci of damage, some forms ofcircumferential cracking, or other defects extending circumferentiallyaround a portion of the pipeline to be detected.

The magnets 1602 in an axial magnetizer may be permanent magnets orelectromagnetic magnets. In an embodiment, the magnets may be rare-earthpermanent magnets. In an embodiment, the magnets may be neodymium-basedmagnets.

Axial magnetizers may be connected to each other with universal joints,which connected to the central shaft by linkage components 1607. Theuniversal joints 1608 may be angle controlled. The axial magnetizers maybe oriented relative to each other to ensure complete coverage of theinside of a pipe. Universal joints 1608 may maintain the orientations ofthe circumferential magnetizers with respect to each other. The centralshaft, linkage components 1607 and universal joints may comprisetitanium to maintain strength, provide corrosion resistance, and reduceweight. In an embodiment, the central shaft, linkage components 1607,and universal joints 1608 may be comprised entirely of titanium.

With reference to FIG. 17, each axial magnetizer may include six magnetbars 1701. Each magnet bar may be designed to cover about 30 degrees ofthe pipe circumference, such that when each axial magnetizer has sixmagnet bars, coupling two axial magnetizers to each other may coverabout 360 degrees of the pipe circumference. Each magnetic circuit polemay include one or more wear pads 1702. A magnetic circuit pole wear pad1702 may protect a magnetic circuit pole from the interior surface ofthe pipeline or debris within the pipeline interior. This may extend theamount of usable time between repairs. In an embodiment, a magneticcircuit pole wear pad 1702 may comprise one or more inserts 1703. In adetailed embodiment, the magnetic circuit pole wear pad 1702 maycomprise a plurality of carbide or ceramic inserts 1703. In anembodiment, one or more magnetic circuit poles may include one or morecarbide or ceramic inserts 1703 disposed directly into the magneticcircuit pole(s). Carbide or ceramic inserts 1703 may provide beneficialreductions in drag force. Carbide or ceramic inserts 1703 may reducedrag force by as much as 30% from conventional designs. Each magneticcircuit pole wear pad 1702, if included, may be maintained at an anglewith respect to the axis of the pipeline. A magnet bar wear pad, in anembodiment, may be arranged and designed to facilitate slowcounter-clockwise rotation of a magnetizer or pig. Alternatively or inaddition, the carbide or ceramic inserts 1703, if included, may bedisposed in a pattern designed to facilitate a slow rotation of the pig.

One or more sensor heads may be placed in each magnet bar. The one ormore sensor heads may be disposed between magnetic circuit poles and maytherefore be positioned to measure magnetic flux through a pipe wall.Each sensor head may include one or more sensors. The magnets maysaturate a portion of pipeline to be inspected with an axial magneticflux. The sensors may measure the magnetic flux and, in particular, maydetect changes or aberrations in the magnetic flux. Defects in thepipeline, including corroded areas, areas missing metal, geometricdeformations, dents, buckles, wrinkles, cracks, and the like may induceaberrations and changes into the magnetic flux, or the magnetic flux mayleak at the particular location of a defect.

The axial magnetizers may travel through a pipe having an internaldiameter less than the nominal diameter of the magnetizer and may beconfigured to closely articulate with the pipe wall. A pipe may havesome structural aberration, such as a crack or crack-like anomaly. Anaxial magnetizer may be particularly adept at detectingcircumferentially oriented aberrations or defects. The magnetic fieldfrom the magnets may be imparted to the pipe wall by front magneticcircuit pole and rear magnetic circuit pole (each having oppositepolarities) to saturate the pipe wall with magnetic flux. Sensors may beplaced between magnets to be within the magnetic field. The magneticfield may be disrupted when the axial magnetizers pass over aberrationsor flaws, and the disruption in the magnetic flux may be detected by thesensors.

In an embodiment, a magnet bar may include a plurality of sensorsbetween each magnetic circuit pole to measure the magnetic flux impartedinto the pipe. The magnetic circuit poles may impart a magnetic fluxinto a pipe wall, and the magnetic flux may flow from one magneticcircuit pole to the other. Sensors positioned within the magnetic fieldmay measure the magnetic flux. In an embodiment, sensors may be spacedat approximately 0.080 inches (2.0 mm). In an embodiment, sensors maycomprise Hall-effect sensors. In an embodiment, an axial magnetizer mayinclude six magnet bars and may have 40 Hall sensors per diameter-inch.Aberrations in the pipe may cause distortions or disruptions in themagnetic field, and the sensors may thus detect the irregularities inthe magnetic field corresponding to the aberration in the pipe. Amagnetizer utilizing an axially oriented magnetic field may be able todetect circumferential flaws of 0.8 inches (20 mm) with an opening of0.004″ (0.1 mm). A sensor head may be able to survive forces of up toabout 20 G, and sensors may be able to withstand pressures of up to2,000 psi (13.8 Mpa) and velocities of up to 30 ft/s (9 m/s).

In an embodiment, each sensor head may include a plurality of sensors.The plurality of sensors may include Hall-effect sensors, eddy-currentsensors, ultrasonic sensors (such as EMAT sensors), or combinationsthereof. The responses of each sensor may be combined and analyzed tolocate or define certain pipeline defects, as discussed above. Forexample, a Hall-effect sensor may detect a response to a magnetic fieldleakage. The output of a Hall-effect sensor may vary linearly ornonlinearly with respect to changes in the magnetic field. These changesmay reflect the presence of a flaw, defect, or anomaly. The output of aplurality of such sensors, in the aggregate, may allow for an ultra-highresolution sampling in a given area of the internal pipe surface,thereby allowing defects to be accurately detected, characterized,analyzed, and quantified. In an embodiment, an axial magnetizeraccording to an aspect of the present disclosure may measure and storeflux leakage values to a sampling density of up to 320 per square inch(50 square cm). In an embodiment, an axial magnetizer according to thepresent disclosure may include several sensor heads, each sensor headhaving a plurality of individual sensors. In an embodiment, a pig mayinclude two axial magnetizer modules with six sensor heads per moduleand 24 Hall-effect sensors per sensor head. In an exemplary embodiment,a smart pig may have a diameter greater than six inches and contain twoaxial magnetizer modules, wherein each module includes six sensor heads.In an embodiment, an axial magnetizer may have a sensor density ofbetween about 30 to 100 sensors per diameter-inch.

An axial magnetizer may be sized to have a nominal diameter slightlylarger than the diameter of a pipe. For example, an axial magnetizerslightly larger than six inches in diameter may be configured to travelthrough a six-inch pipe. One of skill in the art will recognize that anaxial magnetizer according to the present disclosure may be sized toinspect pipes of alternate diameters. An axial magnetizer may includecompression features allowing the magnetizer to fit inside and travelwithin the pipe.

With reference back to FIG. 16, magnetic circuit poles 1603, 1604 maycontact the interior of the pipeline. In an embodiment, magnetic circuitpoles 1603, 1604 may function as a flux coupler to more efficientlysaturate a pipe wall with a magnetic field. In a detailed embodiment,magnetic circuit poles 1603, 1604 may include wear pads 1702 on at leasta portion of a surface that contacts the pipe wall. Wear pads 1702 maycomprise one or more ceramic or carbide inserts 1703, as depicted inFIG. 17. Ceramic or carbide inserts 1703 may protect the magneticcircuit poles 1603, 1604 from wear and may reduce drag force. In anembodiment, ceramic or carbide inserts 1703 may reduce drag force byabout 30%.

Sensor head wear pad 1702 may comprise a nickel-based alloy orsuperalloy. Magnetic circuit poles 1603, 1604 may include a ceramicinsert 1703 or coating. In detailed embodiments, the ceramic maycomprise silicon carbide. In alternate detailed embodiments, the insertsmay comprise tungsten carbide. Other varieties will be apparent to thoseskilled in the art.

The axial magnetizer according to the embodiment depicted in FIG. 18 mayinclude a means for collapsing the magnet bars. Means for collapsing maycomprise front links 1801 and torsion spring 1802. Torsion spring 1802may exert a sufficient force, such as a spring force, to maintain themagnetic circuit poles 1603, 1604 in engagement with the pipe wall butmay collapse, entirely or partially, if the magnetic circuit poles 1603,1604 encounter an aberration in the pipe, such as an indentation, or ifthe pig including the axial magnetizer encounters a bend in the pipe. Inan embodiment, sensor head 1605 is also operatively coupled to the meansfor collapsing by virtue of it being part of the magnet bar.

In an embodiment, a magnetizer may include a magnetizer cushion disposedbetween a central shaft and one or more magnet bars. In an embodiment, amagnetizer cushion may be constructed from a polyurethane or,alternatively, one or more thermosets or thermoplastics. In one aspect,a magnetizer cushion may be annular and may be disposedcircumferentially about the central shaft. In another aspect, multiplemagnetizer cushions may be disposed about one or more circumferentialportions of the central shaft. In one aspect, the one or more magnetizercushions may be disposed at one axial end of a magnet bar. In anotheraspect, the more or more magnetizer cushions may be disposedcircumferentially about the central shaft at each axial end of a magnetbar. In an embodiment, a magnetizer having a magnetizer cushion mightnot have a torsion spring 708; rather, a magnetizer may comprise frontlinks 707, upper link 709, and the magnetizer cushion. The magnetizercushion may provide a force sufficient to bias one or more magnet barstoward a pipe wall. The magnetizer cushion may be constructed orconfigured to have a pre-determined hardness and collapsibility.

A magnetizer cushion may present a number of advantages for biasing oneor more magnet bars against a pipe wall compared to a spring (e.g., asteel torsion spring). First, a magnetizer cushion may provide a forceon the magnet bar that biases the magnet bar against the pipe wall, butthe magnitude of force provided by the magnetizer cushion may besubstantially less than the force imparted to the magnet bar by a spring(e.g., a near neutral force). With a lesser force, the drag experiencedby a magnetizer or a pig incorporating a magnetizer may be reduced.Moreover, with a lesser force, the amount of wear suffered by magnetizerand/or magnet bar components is reduced. Second, a magnetizer cushionmay absorb vibrations or may better absorb vibrations, thereby improvingthe quality of the data gathered by the sensors and improving detectionof pipe defects. Third, a magnetizer cushion may better absorb forcesfrom high-impact events, preventing damage to the magnetizers. Fourth, amagnetizer cushion may be able to be swapped with a magnetizer cushionhaving a different hardness, so a user may be able to control the rideheight and sag factor, which can better tailor the magnetizer fordifferent pipelines or different environments. Fifth, a magnetizercushion may provide additional protection for electronic wiring (e.g.,from shear forces, twisting, or pressure), which may be passed throughthe lower portion of the cushion. Sixth, a magnetizer cushion maysimplify the design of the magnetizer component that biases the magnetbar against the pipe wall; specifically, some spring designs arerelatively complex, subjecting the springs to maintenance (e.g.,replacement, inspection, cleaning). A magnetizer cushion may have anextended life, and may require significantly less cleaning, reducingmaintenance burdens and reducing the risk of component failure. Seventh,spring designs (specifically in larger tools) can be costly; amagnetizer cushion may cost a fraction of a relatively more complicatedspring. Incorporating a magnetizer cushion, therefore, may reducemanufacturing costs and may reduce the cost of ownership long term.Eighth, many spring designs have complex shapes, and debris may build upin and around the spring over time, reducing the function of the springand requiring additional ongoing maintenance. A magnetizer cushion mayreduce or eliminate such build up due to its simpler shape and how ittakes up space where debris may have previously built up.

In an alternate embodiment, sensor head 1605 includes an independentsensor head suspension system. Sensor head suspension system may includeone or more conical springs 1805 coupling the bottom of the sensor head1605 to the magnet bar. In an embodiment, sensor head suspension systemcomprises dual conical springs 1805. Both means for collapsing (and/orthe magnetizer cushion) and sensor head suspension system may enablecomponents of the axial magnetizer to collapse up to 25% of the outsidediameter of the pipe; that is, the diameter of at least part of theaxial magnetizer may be reduced by up to 25% when encountering anaberration in the pipe or when going around a bend in the pipeline.These features may allow a pig to navigate pipeline bends of greaterthan or equal to 1.5 D (where D is equal to the pipe diameter). In anembodiment, these features may allow a pig to navigate pipeline bendswith a minimum separation of 2 D (i.e., two pipe diameters separation).In another embodiment, the features may allow a pig to navigate a pairof 1.5 D bends separated from each other by a pipeline distance equal to3 D. The collapsibility features may reduce drag force on the axialmagnetizer, which may help to prevent a pig from stalling whennavigating a relatively tight bend.

In an embodiment, each magnet bar may include rear links similar tolinks 1801 to join the rear end of each magnet bar to the central shaft,along with a torsion spring or a magnetizer cushion. Such an embodimentmay maintain the entire magnet bar in contact with the pipe wall.Alternatively, each magnet bar of an axial magnetizer may include afront control link 1801 and a torsion spring 1802 or a magnetizercushion. Torsion spring 1802 or the magnetizer cushion may support theweight of each magnet bar and may help to support the weight of thecentral shaft. The rear portion of the axial magnetizer may include apolyurethane ring 1808. Polyurethane ring 1808 may help to maintain eachmagnet bar biased against the pipe wall but may also help to balanceforces, especially when encountering aberrations in the pipeline or whennavigating bends. Polyurethane ring 1808 may include bends 1809, whichmay allow polyurethane ring 1808 to temporarily collapse and allow themagnet bar(s) to collapse toward the center shaft. Ring 1808 may be madefrom polyurethane for durability and chemical resistance concerns;however, one of skill in the art may recognize alternative materialsfrom which ring 1808 may be constructed, such as silicone or a durable,chemical-resistant thermoplastic.

A sensor head may be in the shape of a sloping trapezoid. The approachangle of a sensor head according to such a design may minimize thetransmission of mechanical shocks and vibrations to the sensors andelectronics. Furthermore, such a sensor head design may provide a longerwear life, which may contribute to a longer inspection time of a smartpig between repairs. In an embodiment, one or more sensor heads mayextend radially outward and articulate with a surface of a pipeline totrack the pipeline surface. In an alternate embodiment, sensor head maybe shaped as a parallelogram or a rhomboid.

FIG. 19 presents a cross-sectional side view of an embodiment of anaxial magnetizer. The embodiment of FIG. 19 may include a central shaft1901 running approximately through the axial magnetizer's central axisand providing a central support for other elements. A front universaljoint 1902 and a rear universal joint 1903 may be coupled to respectiveends of the central shaft 1901. Front universal joint 1902 and rearuniversal joint 1903 may couple the axial magnetizer to one or moreother modules of a pig, such as another axial magnetizer, an electronicsmodule, a mapping module, a circumferential magnetizer, or the like. Inan embodiment, front universal joint 1902 and rear universal joint 1903may be able to rotate about central shaft 1901. In an embodiment,central shaft 1901 may extend to universal joint limiter 1907, which maylimit the movement of the universal joints 1902, 1903. For example, iftwo axial magnetizers connected by universal joints have a limitedrotational movement, the magnetizers may maintain a consistentorientation with respect to each other to maintain 360-degree pipe wallcoverage. Front universal joint 1902 and rear universal joint 1903 maybe coupled to central shaft 1901 by a bolt or similar couplingmechanism, about which the universal joints 1902, 1903 may pivot. Theability of universal joints 1902, 1903 to pivot may allow the pig,including the axial magnetizer, to better navigate sharper bends in thepipeline. For example, a pig including an axial magnetizer according tothe embodiment described in FIG. 19 may be capable of negotiating a 3 D(where D is equal to the nominal pipe diameter) pipe bend radius. Inanother example, the pig may be able to navigate a pair of 1.5 D bendsseparated from each other by a pipeline distance equal to 3 D.

An axial magnetizer according to an embodiment such as that illustratedin FIG. 19 may include one or more magnet bars. In an embodiment, anaxial magnetizer may include six magnet bars, each providingapproximately 30 degrees of pipe wall coverage. Each magnet bar may becoupled to the center shaft 1901 at the front end with a magnet bar link1905 at magnet-bar-to-center-shaft connection 1904. Connection 1904 mayinclude a bolt (or other similar coupling mechanism) about which magnetbar link 1905 may rotate or pivot. The ability of the magnet bar torotate or pivot about connection 1904 may allow the magnet bar tocollapse toward the center shaft 1901. In an embodiment, thecollapsibility of each magnet bar may allow an axial magnetizer toreduce its cross-sectional diameter by about 25%. This may allow themagnetizer to navigate tighter turns than would otherwise be possiblewithout becoming stuck or stalled. Without becoming stalled around abend, a pig with an axial magnetizer according to the present disclosuremay be able to maintain more consistent speed—even around tightbends—and thus may maintain more a more complete measurement of thepipeline. In contrast, if a pig stalls around a bend, pressure may buildup behind the pig, eventually shooting the pig forward through the bendat a velocity that is too high to take measurements of the pipeline,thus reducing the quality of the inspection. A torsion spring 1906 ormagnetizer cushion may be included at the connection between the magnetbar and the magnet bar link 1905 to support the weight of the magnet barand to maintain the magnet bar in a biased position against the pipewall, while still allowing for collapsibility when necessary. In anembodiment, a polyurethane ring 1908 may couple the rear end of themagnet bar to the center shaft 1901. Polyurethane ring 1908 may includean outward bend (e.g., a rearward-facing bend), which may allow themagnet bar to collapse toward the center shaft when encountering asufficient force (e.g., a pipe aberration or bend). Polyurethane ring1908 may also absorb shock.

Each magnet bar may include front magnet(s) 1910A. Front magnet(s) 1910Amay have a first polarity. Each front magnet 1910A has the same polarityas the other front magnets, such as front magnet(s) 1910C. Rearmagnet(s) 1910B may have the opposite polarity as front magnet 1910A.Each rear magnet 1910B had the same polarity as the other rear magnets,such as rear magnet(s) 1910D. Each magnet bar may include one or moremagnet shields 1911. Magnet shields 1911 may help to focus the magneticfield from the magnets to allow more efficient transfer of magnetic fluxthrough the pipe wall and, accordingly, more consistent, accurate, andefficient measurements to be taken. Each magnet bar may include a sensorhead 1920, which may include a wear pad, upon which Hall effect sensors1921 may be disposed. Sensor head may further include a sensor board1923 and a sensor head base plate 1924. For example, sensor board 1923may be a printed circuit board providing support and electricalconnectivity to Hall effect sensors 1921. Each sensor head 1920 mayinclude one or more conical springs 1922 coupling the sensor head 1920to the magnet bar. In an embodiment, each sensor head 1920 is coupled toits respective magnet bar by dual conical springs 1922. Conical springs1922 may support the sensor head 1920, may keep the sensor headpositioned against a pipe wall, and may allow for collapsibility whenencountering an aberration or bend in the pipeline.

FIG. 20 provides a sectional illustration of a portion of a smart pigincluding magnetizers according to one or more aspects of the presentdisclosure. FIG. 20 shows a portion of a smart pig 2000 having acircumferential magnetizer module 2001 and an axial magnetizer module2002. Circumferential magnetizer 2001 and axial magnetizer 2002 may eachhave an axially extending central shaft 2003 from which one or moremagnet bars may extend radially about the circumference of the centralshaft 2003. One or both of circumferential magnetizer 2001 and axialmagnetizer 2002 may include one or more magnetizer cushions 2020disposed about central shaft 2003. The one or more magnetizer cushions2020 may maintain a force against each magnet bar, maintaining eachmagnet bar biased against a pipe wall in use. Magnetizer cushion 2020may compress or deform in response to a pipe wall aberration or bend inthe pipe, which in cooperation with links may collapse magnet bar towardthe central shaft 2003, thereby allowing the magnetizer to navigate saidaberration or bend.

FIG. 21 illustrates a front view of a magnetizer cushion 2100 for anaxial magnetizer or a circumferential magnetizer in accordance with anembodiment of the present disclosure. Magnetizer cushion 2100 may beformed of a thermoset material, such as a polyurethane. The materialfrom which magnetizer cushion 2100 is constructed may be determinedaccording to desired characteristics of the magnetizer cushion 2100,including ability to survive in a pipeline environment, hardness,deformability, force imparted to the magnet bars, and the like. In anembodiment, magnetizer cushion 2100 may be a polyurethane cushiondesigned to have a Shore durometer of between about 70 A to about 90 A.In another embodiment, magnetizer cushion 2100 may be a polyurethanecushion designed to have a Shore durometer of between about 75 A toabout 85 A. Magnetizer cushion 2100 may be disposed around a centralshaft of a magnetizer. Specifically, a central shaft of a magnetizer mayextend through a central shaft hole 2101 of a magnetizer cushion 2100.Magnetizer cushion 2100 may have a plurality of holes 2110 disposedtherethrough. Holes 2110 may provide for collapsibility of themagnetizer cushion 2100, allowing magnet bars to collapse toward thecentral shaft when the magnetizer passes over a pipe wall indentation orwhen traversing a bend in the pipeline. One or more inner holes 2111 mayprovide space for certain internal components, such as electricalwiring, to pass through magnetizer cushion 2100. Inner holes 2111 mayprovide additional protection for components such as electrical wiringform shear forces, twisting, or pressure. Magnetizer cushion 2100 mayprovide one or more outer indentations 2120 and/or on or more innerindentations 2130, which may provide for additional compressibility ofmagnetizer cushion 2100. Compressibility provided by one or more of theholes 2110, outer indentations 2120, and/or inner indentations 2130 mayreduce the forces biasing the magnet bars against the pipe wall,particularly when compared to a spring. Such compressibility may imparta force on a magnet bar from about 20% to about 30% less than the forcethat would be applied by a steel spring. With a lesser force, the dragexperienced by a magnetizer or a pig incorporating a magnetizer may bereduced. Moreover, with a lesser force, the amount of wear suffered bymagnetizer and/or magnet bar components is reduced. In an alternateembodiment, inner indentations may engage with a rippled shape of acentral shaft, which may help secure the engagement of the magnetizercushion 2100 to the central shaft and prevent undesired rotation of themagnetizer cushion 2100 about the central shaft. Alternatively oradditionally, outer indentations 2120 may provide similar engagementswith the magnetizer bars.

FIG. 22 is a front sectional view of a circumferential magnetizer 2200incorporating a magnetizer cushion 2201 in accordance with an embodimentof the present disclosure. Circumferential magnetizer 2200 may include acentral shaft 2210 around which may be disposed a magnetizer cushion2201. The magnetizer cushion 2201 may include a plurality of holes 2202,such as holes 2110 described with respect to FIG. 21. One or morespacers 2215 may be located on the forward or aft sides (or both) ofmagnetizer cushion 2201. Circumferential magnetizer 2200 may include aplurality of magnet bars 2220. Disposed within each magnet bar 2220 maybe a sensor head 2230 containing a plurality of sensors.

FIG. 23 is a side sectional view of a circumferential magnetizer 2300incorporating a magnetizer cushion 2301 in accordance with an embodimentof the present disclosure. Circumferential magnetizer 2300 may include acentral shaft 2310 running axially through circumferential magnetizer2300. Surrounding circumferential magnetizer 2300 may be a magnetizercushion 2301 disposed between central shaft 2310 and magnet bars 2320.Magnetizer cushion 2301 may support and bias magnet bars 2320 against apipe wall. Magnet bars 2320 may include a sensor head 2330 containingsensors to measure magnetic flux and flux disturbances in a pipe wall.One or more spacers 2315 may be located on the forward of aft sides (orboth) of magnetizer cushion 2301. Toward the aft end of central shaft2310, polyurethane ring 2340 may be disposed. Polyurethane ring 2340 mayhelp to maintain each magnet bar 2320 biased against the pipe wall butmay also help to balance forces, especially when encounteringaberrations in the pipeline or when navigating bends. Polyurethane ring2340 may include bends 2341, which may allow polyurethane ring 2340 totemporarily collapse and allow the magnet bar(s) 2320 to collapse towardthe center shaft 2310. Polyurethane ring 2340 may also assist withabsorbing shock and vibrations encountered in pipeline environments,thereby helping to protect more sensitive components. Toward the forwardend of central shaft 2310, magnet bars 2320 may be coupled to a link2350, which may be hinged and assist in allowing magnet bars 2320 tomove radially between the central shaft 2310 and a pipe wall (e.g.,collapse toward central shaft 2310), such as when a pipe wall has anaberration or when encountering a bend. Magnetizer cushion 2301 exertsforces on magnetizer bars 2320 to bias them against a pipe wall, butthose biasing forces are less than forces that other components (such assteel springs) may exert on magnetizer bars. As such, magnetizer cushion2301 may contribute to improved collapsibility of magnet bars 2320. Inan embodiment, magnetizer cushion 2301 may be constructed from, forexample, polyurethane and may be configured to possess a particularhardness, such as from about 70 A to about 90 A Shore durometer. Inanother embodiment, magnetizer cushion 2301 may be constructed from, forexample, polyurethane and may be constructed to possess a particularhardness, such as from about 75 A to about 85 A Shore durometer.

FIG. 24 is a side view of a magnetizer cushion 2401 for acircumferential magnetizer along with a forward spacer 2411 and an aftspacer 2412 in accordance with an embodiment of the present disclosure.Magnetizer cushion 2401 may include one or more indentations 2402 alonga circumferential periphery of magnetizer cushion 2401.

FIG. 25 is a front sectional view of an axial magnetizer 2500incorporating a magnetizer cushion 2501 in accordance with an embodimentof the present disclosure. Axial magnetizer 2500 may include a centralshaft 2510, around which may be disposed a magnetizer cushion 2501.Magnetizer cushion 2501 may include a plurality of holes 2502, which mayprovide for collapsibility of magnetizer cushion 2501 and may increasethe protection of sensitive, internal components like electrical wiring(particularly internal holes 2503). One or more spacers 2515 may belocated on the forward or aft sides (or both) of magnetizer cushion2501. Axial magnetizer 2500 may include a plurality of magnet bars 2520.Disposed within each magnet bar 2520 may be a sensor head 2530containing a plurality of sensors.

FIG. 26 illustrates a side view of a magnetizer cushion 2601 for anaxial magnetizer in accordance with an embodiment of the presentdisclosure. Magnetizer cushion 2601 may include an outer periphery 2602extending radially and circumferentially from a central shaft of amagnetizer and configured to bias one or more magnet bars against a pipewall. Beneath the outer periphery 2602, magnetizer cushion 2601 mayinclude one or more holes 2603, which may be configured to impartcompressibility to magnetizer cushion 2601, allowing magnetizer cushion2601 to compress inwardly toward the central shaft (and with it, themagnet bars) when the magnetizer passes over a pipeline aberration ortraverses a bend.

FIG. 27 is a front view of a magnetizer cushion 2701 for an axialmagnetizer in accordance with an embodiment of the present disclosure.Magnetizer cushion 2701 may include an outer periphery 2702, which maycontact one or more magnet bars and dispose the magnet bars against apipe wall. At the interior of magnetizer cushion 2701 may be disposed ahole 2703 through which a central shaft of a magnetizer may be disposed.Magnetizer cushion 2701 may contain a plurality of holes 2704, which mayallow magnetizer cushion to compress (e.g., such that the outerperiphery 2702 or a portion thereof may compress radially inward towardcentral shaft hole 2703). Magnetizer cushion 2701 may also include oneor more interior holes 2705, which, in addition to increasing thecompressibility of magnetizer cushion 2701, may provide protection forone or more sensitive components of a magnetizer. In an embodiment,electrical wiring may be disposed through one or more interior holes2705.

FIG. 28 depicts a side sectional view of an axial magnetizer 2800incorporating a magnetizer cushion in accordance with an embodiment ofthe present disclosure. Axial magnetizer 2800 may include a centralshaft 2810 running axially through axial magnetizer 2800. Surroundingaxial magnetizer 2800 may be a magnetizer cushion 2801 disposed betweencentral shaft 2810 and magnet bars 2820. Magnetizer cushion 2801 maysupport and bias magnet bars 2820 against a pipe wall. Magnet bars 2820may include a sensor head 2830 containing sensors to measure magneticflux and flux disturbances in a pipe wall. One or more spacers 2815 maybe located on the forward of aft sides (or both) of magnetizer cushion2801. Toward the aft end of central shaft 2810, polyurethane ring 2840may be disposed. Polyurethane ring 2840 may help to maintain each magnetbar 2820 biased against the pipe wall but may also help to balanceforces, especially when encountering aberrations in the pipeline or whennavigating bends. Polyurethane ring 2840 may include bends 2841, whichmay allow polyurethane ring 2840 to temporarily collapse and allow themagnet bar(s) 2820 to collapse toward the center shaft 2810.Polyurethane ring 2840 may also assist with absorbing shock andvibrations encountered in pipeline environments, thereby helping toprotect more sensitive components. Toward the forward end of centralshaft 2810, magnet bars 2820 may be coupled to a link 2850, which may behinged and assist in allowing magnet bars 2820 to move radially betweenthe central shaft 2810 and a pipe wall (e.g., collapse toward centralshaft 2810), such as when a pipe wall has an aberration or whenencountering a bend. Magnetizer cushion 2801 exerts forces on magnetizerbars 2820 to bias them against a pipe wall, but those biasing forces areless than forces that other components (such as steel springs) may exerton magnetizer bars. As such, magnetizer cushion 2801 may contribute toimproved collapsibility of magnet bars 2820. Magnetizer cushion 2801 maybe constructed from, for example, polyurethane and may be constructed topossess a particular hardness, such as from about 70 A to about 90 AShore durometer. In another embodiment, magnetizer cushion 2801 may beconstructed from, for example, polyurethane and may be constructed topossess a particular hardness, such as from about 75 A to about 85 AShore durometer.

FIG. 29 is a side view of a magnetizer cushion 2900 for an axialmagnetizer or a circumferential magnetizer in accordance with anembodiment of the present disclosure. Magnetizer cushion 2900 mayinclude one or more indentations 2902 along an outer periphery 2901 ofmagnetizer cushion 2900.

FIG. 30 is an isometric view of an example of an axial magnetizer 3000in accordance with one embodiment of the present disclosure. In anembodiment, axial magnetizer 3000 may include a plurality of magnet bars3010, each of which may contain a sensor head 3020 containing one ormore sensors. Magnet bars 3010 may include one or more wear pads 3021.Underneath magnet bars 3010 and supporting magnet bars 3010 against apipe wall may be one or more magnetizer cushions 3030.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to those skilled in the art.The various aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting.

What is claimed is:
 1. A magnetizer cushion, comprising: a supportmember, the support member including: a forward-facing surface having asubstantially circular cross section and an outer periphery; acentral-shaft hole extending axially through the support member centeredon approximately the center of the support member; at least one innerhole extending axially through the support member and located radiallyoutward from the central-shaft hole and radially inward from theperiphery; wherein the central-shaft hole is configured to receive acentral shaft therethrough; and wherein the support member is configuredto temporarily compress at least partially radially inwardly when atleast a portion of the periphery experiences a compressive force.
 2. Themagnetizer cushion of claim 1, wherein the support member is constructedfrom polyurethane.
 3. The magnetizer cushion of claim 1, furthercomprising a plurality of inner holes located radially outward from thecentral-shaft hole and arranged around the central-shaft hole.
 4. Themagnetizer cushion of claim 1, further comprising at least one outerhole extending axially through the support member and located radiallyoutward from the inner hole and radially inward from the periphery. 5.The magnetizer cushion of claim 4, further comprising a plurality ofouter holes located radially outward from the at least one inner holeand arranged around the central-shaft hole.
 6. The magnetizer cushion ofclaim 1, wherein the at least one inner hole is configured to receive asensitive component therethrough.
 7. The magnetizer cushion of claim 1,wherein the support member has a hardness of between about 70 A andabout 90 A Shore durometer.
 8. The magnetizer of claim 1, wherein theperiphery has a plurality of axially extending indentations.
 9. Themagnetizer of claim 1, wherein the central-shaft hole has at least oneinner indentations.